Bumping this back up. Luke, have you made/seen any changes? When I log the current gear, it always shows "3", but I don't know that it affects anything.
Bumping this back up. Luke, have you made/seen any changes? When I log the current gear, it always shows "3", but I don't know that it affects anything.
Ill post my tune when I get home from work the earthing of the park/neutral wire made no difference that i noticed but my dfco works as it should not sure what ive changed but you can check my tune file against yours
Great, thanks. At some point can you log the current gear as well and see what it reports?
Also probably worth asking - is there anything else in the wiring, like Luke was thinking, that would affect this? My understanding is that the M6 cars don't know what gear they're in (mine always says 3), so I don't know why anything else would matter, but I'm running out of straws to grasp.
Here is my current tune
So ive noticed no change in the P/N wire earthed or unearthed not even the PRND321 changes mines constantly on D. But my DFCO appears to be working fine in gears 3,4,5,6
the first two I think im not able to get enough speed up to enable the DFCO but i havent had enough time to scan and try just yet sorry
I haven't moved to the newer version yet so I can't look at your tune, but I'll do that later.
Question for anyone - my DFCO Active Spark Threshold vs. RPM table has 0-4* worth of spark in the cruising cells. I noticed that a stock file has this at -1*. When I let off the throttle in 4th (in the log in this thread,) timing drops to ~20* but then goes back up. If I set the threshold artificially high, say 21*, would this basically force it into DFCO as soon as I let off the throttle in gear? Would there be any problematic downsides to this? Since a root cause doesn't seem to exist, I'm wondering if being a little more forceful about it would work.
My understanding of the threshold is the degree of advance that must be reached in order to turn the fuel off? so if you set it to 21* then the fuel wouldnt shut off unless you had 21* in your timing advance tables?? I would of thought setting it to 1* would force it into DFCO? or am I arse about with how im interpreting this??? Hope i havent confused myself or you for that matter
I hate to add even more questions but hopefully mine is easy. Up until this thread I thought DFCO was supposed to completely cut fuel- as in 0.0% Duty cycle. Most aftermarket (all?) ECU with a fuel cut scenario operate this way. So, all this time, I've been trying to get my DFCO to go 0% and I haven't seen that happen- so I assumed it wasn't working. Which lead me to research other threads about DFCO which lead me here.
So I get here and I find you guys are seeing a "lean" pulse during DFCO, not a complete fuel cut but in fact simply a lean a/f ratio and some reduced timing. I find that extremely odd- my first question is, are you SURE that DFCO is supposed to work this way?
If so, then my second thought is a possible solution for everyone. In my car, because I assumed DFCO wasn't working, I did the next best thing- I programmed the VE table to 15:1 in those regions where I lift from the throttle at high vacuum. If you are telling me this is the same thing that DFCO does anyways, well then I don't see the difference in doing it in the VE table vs having the algorithm do it for you, except perhaps a reduced delay in activation I suppose.
Correct, AFAIK, but I think I was slightly confused on when the Active Spark Threshold came into affect. Looking at it again -Originally Posted by luke
I think I was misinterpreting this as the number had to fall below that amount, when it reality it's looking for a number over that amount. If the AST table says 3*, then my active spark would have to be > 3* in order to activate DFCO (in addition to the other tables, of course.) So yea, setting the number higher would hurt, not help. There goes that idea.This is the degree spark advance that must be reached to turn the fuel off
I can't speak beyond my experiences here, but my IPW drops to 0.5ms when in DFCO. When I'm in the "problem" gears 4-5-6, no active DFCO, my IPW is still in the ~1.7-2.0ms range. I, like you, leaned out the low kPa cells to at least get a lean off-throttle condition, although it's not the same thing. Spark doesn't drop, which doesn't aid in engine braking. My spark remains in the 20s, but my AFR is leaned out.
Last edited by FD3S; 06-05-2017 at 06:59 PM.
Also finally got around to updating versions and checking out your tune, Luke. I don't see anything in particular in the DFCO tables that would make me think I have something way off-base. Thanks for posting, though.
No worries.... I was going to say just copy my DFCO tables over but if you say yours is pretty close then no need, I was just going threw a few of my logs and was wondering what km/h-m/h you are getting to while testing your DFCO? also do you have a higher than normal idle? eg. 1100rpm +? or a low map reading when at 0% TPS? Im just thinking that maybe these factors are preventing you entering DFCO??
I just looked over your tune I remember reading on this forum that if your transient fuel # is to high that it may prevent DFCO try lowering yours a few Mg at a time and see how that effects DFCO??? Im not to sure if im 100% correct or what other effects this has so if someone else could clarify this and correct me that would be much appreciated....
Im actually still trying to figure out what "transient fuel" does? The description is not very helpful to me, ...
My idle isn't high. I can't remember off the top of my head but it's definitely below 1000. I'm thinking 850ish? I upped the transient fuel when trying to sort through lean between-shift AFR. I know DFCO has never worked for me in 4-5-6, and could try to lower it again for testing purposes, but I'm not sure that would be the problem considering it still works in 1-2-3. It'd actually be more reasonable for DFCO to just not work at all. For it to work in half the gears is just odd to me.
Transient Fuel won't prevent DFCO but it can stop the inj. PW going low enough (sometimes) and for that reason, sometimes it gets reduced to allow the injector pulsewidth to drop enough on the overrun (in or out of DFCO).
EDIT: one more point,: seems obvious to me but maybe not...You have as far as I know to be clearly decelerating for DFCO to kick in. That happens easily and more or less by default in low gears. In higher ones you have to be getting a bit of a move on for it to happen (e.g. high throttle to 6000 rpm in 4th and shut off, lol, thats a bit of an extreme example).
Last edited by dermotw; 06-10-2017 at 01:17 AM.
99 TA, Texas Speed LS376, PRC heads, 233/239 cam, Fast 92mm, 95mm TB, card style MAF, Tick TR6060, Strange 4.11 12 bolt axle & clutchpack diff, Strano springs/dampers, Vette 18" wheels, Vette disks, CTS-V calipers, 16lb flywheel, long tube headers, no cats.
well I really like the idea of shutting off injectors completely, and i think it is terrible to run them " a little". If the injector fires a tiny bit (not enough to burn in the cylinder) then the fuel washes into the exhaust and burns there- making the decel sound like *poppadopaapooppopopooopopp* basically it sounds terrible. I will experiment with dfco and map strategies which allow complete shutting off of the injector and report back if i make any progress.
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